Thiodiethanol is a well known diol, the hydroxyl groups of which exhibit unusual reactivity because of their positioning beta to a sulfur atom in an aliphatic chain. Unlike alkanediols, such as 1,4-butanediol, thiodiethanol quite readily undergoes an autocondensation reaction under the influence of heat and certain acidic dehydrating catalysts, such as hydrogen chloride. This was shown by Ballard et al, U.S. Pat. No. 2,484,369. Low molecular weight, rubberlike materials, indicated as (I) in the following reaction scheme, were obtained: EQU (n+1) S(C.sub.2 H.sub.4 OH).sub.2 .sup.H HO[C.sub.2 H.sub.4 SC.sub.2 H.sub.4 O]nC.sub.2 H.sub.4 SC.sub.2 H.sub.4 OH +nH.sub.2 O (I)
Woodward et al, J. Poly. Sci. 41, 219-23; 225-30 and 231-239 (1959), studied the acid-catalyzed autocondensation of thiodiethanol with hydrochloric acid and phosphorus pentoxide, and copolymerization thereof with aliphatic hydroxy compounds. Hydrochloric acid provided low molecular weight, waxy, water-soluble polymers in addition to ring closure to thioxane. Phosphorus pentoxide afforded products ranging from viscous liquids to rubbery waxes. Some indication of copolymerization with diethylene, trimethylene and butylene glycols were found. However, no useful rubbery polymers were observed.
Thiodiethanol has been copolymerized with equimolar amounts of 1,6-hexanediol in the presence of p-toluene sulfonic acid to give low molecular weight waxy polymers (Holtschmidt, U.S. Pat. No. 2,998,413); with triethylene glycol, 1,6-hexanediol and trimethylol propane in the presence of phosphorous acid to give low molecular weight polymers useful as polyurethane intermediates (Holtschmidt, French Patent No. 1,373,471); with thiodipropionic acid to give hydroxyl terminated low molecular weight polymers suitable for polyurethanes (Holtschmidt, German Patent No. 1,045,641). These products have been reacted with aromatic diisocyanates to provide polyurethane elastomers; see, for example, U.S. Pat. No. 2,862,962; French Patent No. 1,373,471; German Patent Nos. 1,007,502, 1,045,641 and 1,108,903 and British Patent Nos. 791,854 and 818,359.
However, neither the autocondensation of thiodiethanol, nor co-condensation with aliphatic diols, has resulted in rubbery products which were useful. Moreover, elastomers derived from thiodiethanol, other than the polyurethane elastomers described above, have not been disclosed.
The present invention represents the culmination of a long series of investigations, conducted largely by the inventor, directed to preparing vulcanizable elastomers based on copolymers of thiodiethanol.
Accordingly, it is an object of this invention to provide vulcanizable elastomer compositions based on copolymers of thiodiethanol.
An additional object is to provide useful elastomers from such compositions.
A further object of the invention is to provide elastomers which have low temperature flexibility and resistance to hydrocarbon oils.
It is yet another object of the invention to provide a method for preparing said elastomers.
Additional objects and advantages will be set forth in part in the description which follows and in part will be obvious from the description or may be learned by the practice of the invention, the object and advantages being realized and attained by means of the compositions, processes and improvements, particularly pointed out in the appended claims.